cxgb4: Detect and display firmware reported errors

The adapter firmware can indicate error conditions to the host.
If the firmware has indicated an error, print out the reason for
the firmware error.

Based on original work by Casey Leedom <leedom@chelsio.com>

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>